POV-Ray : Newsgroups : povray.general : an extraordinary rotation question : Re: an extraordinary rotation question Server Time
30 Jul 2024 14:28:48 EDT (-0400)
  Re: an extraordinary rotation question  
From: mysdn
Date: 20 Jun 2009 20:55:00
Message: <web.4a3d831bcfb6d60e4e47a1b0@news.povray.org>
Tim, I have some final questions. Then I think I'll comprehend the whole logic
involving rotations. I feel pretty stupid after all these explanations but I
feel if I get an answer to this list everything will fall into place. By the
way this whole concept is not so easy to grasp without some handholding.
I'm already grateful for all the answers.


in a previous post I asked you where did you come up with the numbers you did.

1- In the example you provided one of the corners is
at <-49.999,-49.999,0.001>, and another at
<50.001,50.001,100.001>.
1- Where are these numbers showing in my sample?

2- When you scale you are relocating the corners around the origin by
multiplication. So
0.01*<-49.999,-49.999,0.001> = <-0.5,-0.5,0>, and
0.01*<50.001,50.001,100.001> = <0.5,0.5,1>

2- Why do you multiply 0.01*<-49.999,-49.999,0.001> = <-0.5,-0.5,0>, and
                       0.01*<50.001,50.001,100.001> = <0.5,0.5,1>


3- So then you have your first wall so you scale by
<250,260,10>*<-0.5,-0.5,0>= <-125,-130,0>, and
<250,260,10>*<0.5,0.5,1>=<125,130,10>

3- Why these 2 multiplications take place?

4- <-0.5,-0.5,0> is the coordinate of of the lower-left-forward corner
of the BOX mesh, which is the _box mesh <-49.999,-49.999,0.001>
scaled by 0.01 (and rounded a bit).

4- Where does it say <-0.5,-0.5,0> is the lower left forward corner of BOX?

5- So the first wall is equivalent to
box{<-250,0,-3.5>,<0,260,6.5>}

5- is <-250,0,-3.5> translate or scale, same question for >,<0,260,6.5>

6- So for this example I'll pick a corner... <-100,-130,0>
6- Which corner is this and how did the number came to be <-100,-130,0>


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